This invention relates a polyamide resin composition excellent in mechanical strength and moldability, which is suitable as a material for producing parts having a complicated shape or for use in a low melting point alloy fusible core method, and a molded product thereof.
A polyamide resin is generally excellent in properties such as mechanical properties, heat resistance and wear resistance, and has been widely used for industrial use including mainly automobile parts and electric parts. Accompanying with it, the usable field of the resin is now further expanding more and more, and resinification of parts having a complicated shape which had been considered to be impossible to resinify has now been carried out. Particularly, in automobile parts, a tendency of resinification in place of metal parts is noticeable in order to lighten the automobile body for improvement of fuel efficiency, decrease costs or improve characteristics such as sound insulating property and heat insulating property, whereby uses of the polyamide resin are increased more and more.
On the other hand, in the field of molding techniques, in order to keep up with production of complicated parts, a fusible core method has ben known as an integrated injection molding method for complicated shapes. This method is a method in which a resin is molded by using a low melting point alloy as a mold core and then the molded product is obtained by melting away the alloy. The method has been employed for the molding of parts having a hollow portion of an undercut portion, particularly engine suction parts such as an intake manifold, a surge tank, or pump parts.
However, when resin molding is carried out by using the fusible core method, if the objective parts are complicated, there are problems that resin molding is difficult since deformation of the core occurs due to pressure at the resin molding or surface failure of the molded product is sometimes generated, and further the alloy is attached and remains on the resin inner surface after dissolving out the core alloy.